My passenger air vent in my 2011 Sport sounds like something is lightly flapping inside, like a little piece of paper or something. How hard is it to take apart, inspect and fix?

 

Sounds like something may be in the blower fan. Easy to check. I don't remember the exact steps but search and you'll find them. Open the glovebox and drop it down. I think you squeeze it in and get it past the rubber stops. Look inside and you'll see the cover for the cabin filter. move the tab to release and pull it out. Put your hand in (car off and fan off), and the fan is there. Feel around and see if anything got past the cabin filter. I wouldn't be surprised (from experience) if a mouse ate through your filter and some of his nest is sitting in your fan/blower. If so, pull the junk out and then try to vacuum what remains. Have a new filter on hand to replace the old one with.

 

MICE!!!

I just checked my cabin air filter and found seeds, fuzzy stuff, and noticed that the mouse chewed up part of the "wallet" that holds the owners manual / service records. The corner of the owners manual was chewed on too.

I agree, take everything out of the glove box, push in on both sides of it at the top corners to disconnect from the dash, swing down. Lightly push in (towards the center) on the tabs that hold in the cabin air filter. Slide it out. Reach in there to see if there are tree leaves / mouse nest materials, then get your hand out of there and run the fan to see if it dislodges anything that's making the noise.

We constantly have mouse problems with both Hondas (CIVIC & FIT) and one is in the garage and one is sitting 30 ft away in the driveway. Honda ought to patent there "system" as a mouse trap. Certainly draws them in.